DE 44 47 645 C2 relates to a process for the preparation of a molded part, especially an interior trim part or the like for motor vehicles, prepared from a non-woven fabric preimpregnated with a thermoplastic resin, in which the non-woven fabric is heated two-dimensionally in a contact heating press beyond the softening temperature of the thermoplastic resin, and predensified, and this non-woven fabric is pressed under a high pressure and at a temperature of from 100 to 130° C. in a hot-press mold, and the pressed molded part is cooled in at least one cooling step, wherein at least a contact pressure is maintained between the cooling mold and the molded part in said at least one cooling step, wherein a film or other decorative material is backed onto the pressed molded part by heating said film or other decorative material and the surface to be backed of the molded part by contact heat and adjoining them under a low pressure, whereupon the pressed molded part provided with said backing film or other decorative material is cooled.
DE 44 00 388 C2 relates to a process for the preparation of a molded part, especially a trim part for a motor vehicle, consisting of at least one support layer and a backing layer, wherein the flat layers are mutually oriented in parallel extension, and the edges are kept at a distance while the edge is separated off, and the layers are pressed together between two press-mold surfaces to become bonded to one another, whereupon the edge opposite to the processed edge of the support layer is contacted with the support layer and attached thereto, characterized in that, immediately after the edge of the support layer is separated off and the two layers are pressed together, the prominent edge of the backing layer is folded around the processed edge and pressed onto the back side of the support layer, while the molded part still contacts the assigned press-mold surface with its front side.
DE 196 07 781 A1 relates to trim parts for automobiles, which are mostly layer materials with a base and a textile decoration. For technological reasons, the latter has consisted of polyester fibers to date. In contrast, for reducing the number of polymers in a particular overall structure, polypropylene fibers are employed. This is enabled by a novel backing method and a special heat control in the process and preliminary backing of the decoration.
DE 199 59 654 A1 describes a process for the preparation of interior trim components of motor vehicles with a defined surface profile, wherein in a first step a material (1) forming the visible surface is positioned in a mold cavity and shaped under the action of pressure and/or temperature to generate the desired surface embossing, in another step a support material (2) based on natural-fiber reinforced polymer materials is shaped into said mold cavity, edge portions of the material (1) not being covered by the support material (2), followed by demolding the interior trim component from the mold cavity upon bending the edge portions of the material.
In DE 43 05 847 A1, an interior trim for a building body and a process for the preparation thereof is described. The trim has a trim base plate including a base material and a first exterior layer material that has been backed onto the base material or bonded thereto in a laminate fashion. The trim base plate is subdivided into a plurality of adjacent surface portions by means of at least one recess. At least one of the surface portions serves as a built-in part. At least one decorative part is adhesively connected with the trim base plate and comprises at least one rigid base plate designed in a shape matching the built-in part, and at least one second exterior layer material that covers the base plate. At its peripheral portion, the decorative part is provided with a flange which is tightly fit into the recess of the trim base plate. The flange embraces the rigid base plate. The above mentioned trim is prepared by a process which comprises the following steps:
(1) placing a base material onto a first mold part of a press mold, wherein the base material is subdivided into a multitude of adjacent surface portions by means of at least one recess, and wherein at least one of the surface portions serves as a built-in part; (2) placing a decorative part onto said second mold part of the press mold, wherein the second mold part is facing the molded part.
DE 103 33 161 A 1 describes interior trim components of motor vehicles having a defined surface profile.
WO 90/03256 relates to a device and process for the preparation of solid products having a defined surface from a fiber-reinforced component support, which are pressed in a one-step process with cycle times of from 40 to 60 s.
WO 01/41999 A1 relates to a method for the preparation of interior trim components of motor vehicles having a defined surface profile, wherein in a first step a material constituting the visible surface is positioned in a mold cavity and molded by the action of pressure and/or temperature while the desired surface impression is simultaneously produced, in a further step a support material based on natural-fiber reinforced polymer materials is inserted in the mold cavity followed by molding, edge portions of material not being covered by support material, followed by demolding the interior trim component from the mold cavity upon bending the edge portions of the material.
All the processes of the prior art have in common that both the building support and the decorative layer are heated to a (high) backing temperature in order to bond the two parts together. Also, the prior art does not allow the use of a plurality of different portions of the decorative layers with a respectively defined surface and/or color profile that are applied to an integral support material.
WO 2005/009721 A1 describes a process for the preparation of interior trim components of motor vehicles having a defined surface profile. The process is realized by preparing the component support on the basis of natural-fiber reinforced polymer materials and adjusting its surface temperature on the surface to be provided with the decorative layer to the desired backing temperature within a range of from 150 to 180° C. in a first step;    the visible side of the decorative layer is heated to the desired graining temperature within a range of from 200 to 220° C., and the backing side of the decorative layer is heated to the desired backing temperature; and    subsequently the component support and the decorative layer are pressed in a mold whose upper part has a structure of said defined surface profile.
Especially Japanese automobile manufacturers make use of the possibility of embossing grains onto decorative materials, mostly for instrument panels, but also for door trims. However, these components constantly do not show any high qualities of the grains and fail to meet the requirements demanded by manufacturers of high quality vehicles in this respect.
In order to be successful in the premium segment of motor vehicles with the so-called in-mold graining method and corresponding interior trim components, the process and the thus obtained interior trim components must be designed in such a way that even the finest grain structures in the embossing mold are taken up by the film, and thus an ideal grain formation and thereby an optimum surface on the component are formed.
Meanwhile, with the process published in WO 2005/009721, it has become possible to image even geometrically complex and very finely structured grains (most extreme example: reproductions of true leather grains) and to produce radii of up to 2.5 mm, while radii of only about 5 to 6 mm are possible with classical backing processes.
Therefore, the automobile manufacturers of premium vehicles are much interested in the in-mold graining methods and corresponding interior trim components. Due to the good grain formation and, above all, the narrow (formerly typical of PUR skin processes) radii, the technology is now directly competing with the PUR skin, which is subsequently back-foamed with PUR.
However, the PUR technology currently has an essential advantage: Since the skin can be prepared in two colors due to the nature of the process, wherein color ranges are separated by a very narrow groove and painted in two colors in an in-mold coating process, or sprayed with PUR systems colored in two colors, integral surfaces with, two or more colors can be produced and subsequently connected with a support part.
However, in the in-mold graining process of the prior art, only two components can be prepared separately and subsequently connected in a suitable joining process, for example, by welding or adhesive bonding. However, these joining processes are very cost-intensive, and double materials (and thus added weight) appear in the region of the joining surfaces. In addition, courses of gaps and transitions to the interior door panel must be matched tediously, which can be realized more easily with an integral support.
Accordingly, an object of the present invention was to provide a process for the preparation of corresponding interior trim components of motor vehicles, especially multicolored components.